Phenotypic disparity and adaptive radiation in the genus Cladia (Lecanorales, Ascomycota)

Phylogenetic relationships of the genera Cladia, Heterodea and Ramalinora were reconstructed using a combined dataset of ribosomal nuclear ITS and LSU and mitochondrial SSU, and protein-coding Mcm7 DNA sequences. Maximum likelihood and Bayesian analyses strongly supported a monophyletic group in which the species of the foliose genus Heterodea and the crustose genus Ramalinora were nested within the fruticose genus Cladia. Alternative hypothesis testing rejected an independent status of Ramalinora. We tested the hypothesis that an adaptive radiation led to the morphological disparity found in the Cladia clade. Gamma-statistics indicated a significantly disproportional clustering of origins of extant lineages at the base of the Cladia clade and lineage-through-time plots were also consistent with the hypothesis of an adaptive radiation at the base of the Cladia clade. Ancestral-range reconstructions supported an origin of Cladia and the three major lineages within Cladia in Australia. On the basis of these results, we propose an evolutionary hypothesis for the genus. The results suggest that processes of adaptive radiation of the ancestor of Cladia in Australia led to the morphological disparity in the extant taxa, and that the broad distribution of some extant species is due to subsequent long-distance dispersal.